Hydrocarbon synthesis process



March 17, 1953 W. A. HORNE ET A1. 2,632,016

v HYDROCARBON SYNTHESIS PROCESS Filed Dec. 2s, 1949 Patented Mar. 17, 1953 HYDROCARBON SYNTHESIS PROCESS William A. Horne and Vincent L. Crawford, Oakmont, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware Application December 28, 1949, Serial No. 135,494

(Cl. Zim-449.6)

9 Claims.

This invention relates to the pro-duction of hydrocarbons by the reaction between hydrogen and carbon monoxide. More particularly, the invention relates to a process for the production of hydrocarbons from hydrogen and carbon monoxide utilizing a series of fixed catalyst beds.

In the production of hydrocarbons, for example hydrocarbons containing three or more carbon atoms such as hydrocarbons boiling within the gasoline and gas oil boiling ranges and wax hydrocarbons, by means of the reaction between hydrogen and carbon monoxide, problems arise because of the highly exothermic nature of the reaction and because of the economic necessity of maintaining long catalyst life. In the past, attempts have been made to solve the problem of temperature control by using a reactor comprising a plurality of catalyst tubes of relatively small cross-sectional area immersed in a liquid cooling medium. This has not proved to be an entirely satisfactory solution to the problem, both because of the high initial cost of the equipment and the high maintenance costs which are especially serious when catalyst change becomes necessary.

It is important in carrying out the reaction that the catalyst remain effective for long periods before regeneration is necessary and that it be capable of being used in a plurality of onstream periods. Operations which tend to reduce catalyst life are undesirable not only because of the catalyst and change-over costs but also because of the time required to bring the system completely on stream.

The process of the invention should be carried out so as to obtain high conversion of carbon monoxide as it passes through a catalyst bed, preferably at least 98 per cent, and ordinarily a run should be stopped when the conversion has fallen to below 95 per cent. High conversions are important because any carbon monoxide that has not been converted to useful products in a process of this type cannot be recovered effectively.

We have discovered in accordance with our invention that carbon monoxide can be eiectively converted, long catalyst life obtained, and the exothermic reaction can be controlled in relatively simple equipment by carrying out the reaction between hydrogen and carbon monoxide, as described below. In its broader aspects this process comprises the use of any synthesis catalyst such as a cobalt or iron catalyst. However, iron catalysts are preferred and the following description will largely be concerned with such catalysts. The preferred embodiment comprises passing into contact with a series of beds of iron synthesis catalyst maintained at hydrocarbon synthesis temperatures and superatmospheric pressures a reactive gas mixture comprising hydrogen, carbon monoxide and recycled gases, removing partially reacted gases from each of the catalyst beds, removing a side stream of partially reacted gases from between catalyst beds while passing the main stream of partially reacted gases towards the succeeding catalyst bed, cooling the side stream, introducing make-up gas comprising carbon monoxide into the side stream, mixing the side stream to which make-up gases have been added with the main stream of partially reacted gases, passing the partially reacted mixture at a hydrocarbon synthesis initiation temperature to the succeeding catalyst bed, while varying the amount of cooling of the side stream in accordance with variations in temperatures of the succeeding catalyst bed.

The reacted gases are removed after the last catalyst bed and are cooled to condense at least the normally liquid hydrocarbons and other compounds boiling above said hydrocarbons. Preferably the condensation is carried out to condense most of the C4 and heavier hydrocarbons and oxygenated compounds formed in the reaction. The remainder of the reaction products in gas phase under these conditions is separated into a portion for recycling and a portion which is removed from the system. The recycled portion is then admixed with fresh feed gas, preferably heated to about the temperature required for initiation of the desired reaction, and passed into contact with the catalyst.

A long useful catalyst life is obtained when operating as described if the temperature gradients across the catalyst beds are controlled. EX- cellent results are obtained with the gradient in the range of about to 200 F., and preferred results are obtained with a range of about to F. The initial and final catalyst bed temperatures depend upon the space velocity, charge composition, the iron catalyst employed and its activity. The minimum hydrocarbon synthesis initiation temperature should lie within the range of about 430 to about 525 F. and the maximum temperature at the exit side of the catalyst bed should be maintained between about 610 to about 630 F.

We have found that the heat which is furnished by the exothermic reaction may be controlled by cooling the side stream from the discharge temperature of about 610 to about 630 F. to a side stream temperature of as low as about 100 F. or even lower. However, it is generally unnecessary to cool the side stream below 100 F., which is a temperature that is easily attained. In so cooling, the normally liquid hydrocarbons and oxygenated compounds produced in the reaction are liquefied and these may readily be removed from the side stream.

The life of the catalyst is also directly affected by the m01 ratio of hydrogen to lcarbon monoxide in the gases fed to the series of catalyst beds. In the presence of recycle gases which contain hydrocarbons, oxygenated compounds, and diluents such as carbon dioxide and water, the catalyst will have an especially long useful life with temperature gradients such as those described above if the hydrogen to carbon monoxide mol ratio of the reactive gas fed to the beds of catalyst vis maintained at more than 15:1 and preferably from 15:1 to 30:1.

In order to maintain the hydrogen to carbon monoxide ratio above the desired 15:1 ratio or in order to maintain it at a constant value in each of the beds, the make-up gas may comprise hydrogen and carbon monoxide. This make-up gas introduced between beds may be of a constant or variable hydrogen to carbon monoxide ratio. In this Way the ratio of hydrogen to carbon monoxide of the partially reacted gases may be kept constant by introducing hydrogen and carbon monoxide in the same ratio at which they are consumed in the reaction or the ratio may be increased or decreased as desired by varying the ratio in the make-up gas. Synthesis gas with a xed hydrogen to carbon monoxide ratio may be introduced between each bed and a separate Vsource of vhydrogen and carbon monoxide may be furnished for making adjustments.

By operating as described, the catalyst can remain on stream for an extended time and it may be subjected to a plurality of regeneration and on-stream periods. In addition, the liquid products removed from each bed may be separately cooled. The liquid products obtained from the later beds vor higher invheavier hydrocarbons, and thus separating the liquid products from the various catalyst beds makes the subsequent processing and fractionation of these products much more simple. If desired, however, it is not necessary to remove liquid products from each catalyst bed. Instead this may be done at intervals or all of the separation of produ-cts may be carried out after thelast catalyst bed.

Either the degree to which the side stream is cooled or the amount of gases removed in the side stream should be varied depending upon the temperature of the make-up gases which are added and the desired temperature in the succeeding bed. We have found that the degree of `cooling of the side stream orV the amount of gases removed in the side stream, or b oth, can beeffectively controlled by the temperature in the succeeding bed in the series.

In general, with a reaction initiation temperature of from 430 to about 525 F., a temperature of the gases leaving the bed of 610 to 630 F., the maximum cooling gradient in the side stream will be from 510 to 530 F. Under these conditions with an initial composition of from 2 tol 3 per cent carbon monoxide and consuming from 2 Vto ,3 volumes of hydrogen per volume of carbon monoxide, from about l5 to about 35 per cent of the total gas stream may be withdrawn and cooled. In the later beds the partially reacted 'gases will containa larger amount of heavier hyside stream may be increased by reducing the amount of cooling which is performed upon the side stream, but it is desirable to cool the gases sufhciently to remove the more volatile hydrocarbons and the oxygenated compounds with low boilingr points in order to obtain the previously mentioned advantages of simpler fractionation which result when liquid products are removed from each of the beds.

It is a feature of our invention that a portion ofthe first reaction products may be removed, asvdescribed, from the separator after the rst catalyst bed and from the separator after each of the subsequent beds. rhe reaction products removed from the earlier beds contain a larger percentage of lower boiling materials than those removed from the later beds.

A typical method of carrying out the preferred embodiment will be described in connection with the accompanying drawing in which the single figure is a simplied now sheet of a reactor system in accordance with the process of our invention. Referring to the drawing, the fresh feed comprising in this case hydrogen and carbon monoxide is fed into the system under pressure at a controlled rate through valved line 5 which leads to line 6 in which are flowing recycle gases, as will later be described. The recycle gases will comprise in addition to butane, propane, ethane, methane and the corresponding,unsaturated hydrocarbons; oxygenated organic compounds; carbon monoxide; hydrogen; carbon dioxide; and normally a small amount of nitrogen. These gases will be saturated with water vapor and the proportions in which the several compounds are present in the recycle gases will depend upon the specic conditions employed in separating the gases for recycling from the product gases. Also, because the separation is not clean cut, there will be traces of heavier hydrocarbons.

The mixture of fresh feed and recycle gases is passed through a gas heater 1 wherein the temperature of the gases is preferably raised to the temperature maintained at the top of the first catalyst bed, for example a temperature between about 430 and 500 F. The heated gases are passed from the gas heater through line 8, vto a pressure control valve 9 actuated by control means II, and then to a reaction vessel I2 containing a number of similar solid beds of catalyst I3, I3a, etc. The catalyst bed I3 is supported on a suitable foraminous support I4 and can if desired be confined at its upper surface by a similar foraminous member I6'.

The heated gases are introduced at a selected rate such as to obtain a desired initial space velocity; for example, a space velocity (volume of feed gas at standard conditions per volume of catalyst per hour) of 300 or greater. The ternperature at the top of catalyst bed I3 is maintained at about the temperature of the entering gases. On passing through the rst catalyst bed, the desired synthesis reactions take place resulting in the evolution of considerable heat. Because of the volume of gases in the charge mixture that does not take place in the reaction, running away of the temperature of the catalyst bed is prevented. However, under conditions describedgfthere is an increase of temperature from Thus the temperature at the bottomfof'theirst bed may lie within therange 'ofabout 610 to .630 F. At the bottom Oi' the catalyst bdthe a part of the gases passes down throughitand the remainder of the gases is removed through side stream line i8 which is perforated throughout its length Within thereaction vessel I2 and extends out of the reaction vessel. "I'hegasesin side stream. line IS are passed throughheat exchanger I9 which is controlled as described below. The partially cooled gases Which'are'thencooled to a temperature of the order cf'abou't 50 to 150 F'. are then passed through a separator 2 I'Wherein the first liquid products are removed byline 22.

The remainder of the gases is passed out of the separator 2! by means of return line 23. Make-up gases are added by means of' line '24"from the synthesis gas manifold 25 by means of valved line 26. The rate of addition of synthesisgas is controlled by control valve 2'! actuated by iioW control means 28. rFhis control means may be adjusted to supply a constant amount of make-up gas or it may be made to respondto diierences in pressure in the side stream line 23. A 'controlled amount of hydrogen from valved'line 29 connected to hydrogen manifold A(ill, 'or a 'controlled amount of carbon monoxide from valved line 3| connected to carbon monoxide manifold 32, or a controlled amount 'of each of these gases may be mixed with the synthesis'gas from valved line2 to form make-up gas inline 24. After the make-up gases have been added, the mixture of gas is passed back into the reactor at'apoint beneath the foraminous plate l1. .The'gases are then thoroughly mixed andare introduced into the second catalyst bed i3d.. Near the bottom Vof this bed there is positioned a temperature sensitive means 33 connected by appropriate control means 34 to control valve 3B whichwcontrols the amount of cooling Water passing through'the heat exchanger i9 previouslyrnentioned and thus controls the amount of cooling given to thegases introduced ,immediately above the second catalyst bed i3d.

The `gases then pass .in like manner Athrough `a series ofcatalyst beds. Each ofithe beds contains a temperature responsive means Whichin .accordance with variations in temperature in that bed varies the cooling in the side stream from the bedfim 1iatelyabove it. The 4liquid products condensed in veachzof theseparators'areremoved v.and fractionated.

The gasesremoved from'the last 'catalyst bed inthe reactor i2'are passed .through .line 31.110 heatexchanger 38 and through line s39 to cooler Ill Where they are Yfurther cooled toa'temperature of no more than 120 F.; for example, toaiternperature between about 60 .and`about.12@F., the

.specic temperature being :sufiiciently .low to cause condensation of the desired products. The cooledproducts are .then .passed through line'd to a separator i3 yof conventional'i'design. Inthis vseparator anaqueous layer and 'aliqud .hydrocarbon layer are formed. The hydrocarbons that are liquid under these .conditions 4are removed from the system throughline 45 andtheaqueous layer comprising a solution -of oxygenatedfcom- Y(iii f--pounds,ffsuchiasalcholssandiketones-isrremovd through line 44.

"YI-he lremai'ning .fgasepusiproducts fare v`'passed -fromtheseparatorthroughalineiIH `and afporton off them: is *vented:.frcmfthesystem :throu'ghline mli.' .l 4e;rporitionlventedisLregulated toholdvsys- :150 .pounds 's perasquare tial 'or-complete :reduction prior ztozbeingxcontactedwith'ithe :reactorxieed .This :can abe :ac-

complished in the system shownibyintroducing hydrogen Lthro ugh :lin'ep ,i .raising the temperature :of theshydrogen in :heater `'I to a ztemperature, for iexample, fof zthe order-:of f 600.to 950' 'F. .and r-thenp assing itheiheated gasithrough the reactor. 'The Agases'iproduced .in this Yreducing "procedure mayb eremoved fromthefrsystem from ithe bottom "o'f 'the ir'eaction Ivessel i12 `through :by-pass line 251i.

The method of the.: invention @may be rvare'd :inxia number lLof .-ways For iexample, r instead v.'.o'f Jcontrollingtheamountofi cooling :Water .which .is zintroduceditothe'heatzexchanger i9, theamount fof gas'lvzhich :is '.'removedtiniside stream-:18 .may instead for.: in y:addition .tbe .regulated by valve :55 ini this ''lne 'which is operated I by :'fcontrol: means 'f1-55. v"Thiscontrol `:peanaflflike *.controlimeans 34 which con'trols`the .cooling 'Water @to ...heat s exchanger lil, is y:actuated :bytemperaturexsensitive "meansS ini-the nextfbed. .'Thezamount'offcooling is controlledV inf thesubsequentfbeds. in atsim- 'ilar manner.

When the/catalyst fus'edlin th'e variousbe'ds `-isi being "ftreat'ed.' fior rexample When lit iis being '"regenera'ted, variousc'ontrol instruments can be `-byfpasse`d. Inprderito also reduce the resistance vvhich:occurs-because of `the'foraminous plates l1,

valvedfbypasslines"53can beplacedlimmdiately -above and "below the foraminous plates.

A"The :iron v"synthesis catalysts 'employecl- Iin lthel present process "can be in `the completely oxidized.partiallyloxidizedfor completely reduced state and-can; if desired, beem'ployed inc'o'njurrc- `tion withV suitableprorrroterssuchias alumina'and potas'siurnoxide.andican 7be disposed on "suitable supports suchasffullers" earth,v activated'alumina, .acid-.treated .moritmorilloniterclays .andilthe like. .Iron .catalysts ...prepared `-.by..,precipita'tion Yof iron :oxide: are .particularly valuable, especially. When :employed .in .the .unpromoted Astate. ..The..extent tof. reduction` o-:these .catalysts has r.an important .eiiect :.uponstheir valuefin .-.the .process -fsuperi'or'mresults .are obtained `:when the catalyst Ihasbeenfrom F10 to '100 perecentsreducedirom :the oxide .andgpreferablyffrom'to 1100g-percent Areducedffrom the-oxide. .Theeffectof.the:extent -of 'the freductioneof the catalyst. is felt .most .fstronglyduring:thefperiod when :the .unit is being placed onistrearnalthough this eXtent-ofae'duc- -tion'also has;an'importantieffect;onthe character :fof ithezproduetsobtained. sni'thisaconne'ctio'n, :.'it .willbezundersto'odfithat thefrcataly'st `will'usually 7 be reduced in the synthesis unit as described above.

As previously indicated, if the maximum temperature is controlled, excellent results are obtained in the present process by maintaining a substantial temperature gradient across the various catalyst beds. The process of our invention has the advantage that as the partially reacted gases are passed through a series of catalyst beds, the amount of diluents formed and the products formed are such that the temperature gradient which occurs in the beds decreases. However, by controlling the amount of cooling which is performed upon the side stream removed before each bed, a substantially constant temperature gradient can be obtained throughout each of the beds used in carrying out the reaction. This has the advantage that the catalyst beds will have practically the same useful life and therefore it will not be necessary to shut down the f process because one or more of the catalyst beds require regeneration before the remaining beds require this action.

There will now be described a presently preferred method of carrying out the process of our invention. These runs are carried out in a reactor about feet high with an internal diameter of about 6 feet. In the reactor there are seven catalyst beds which are equally spaced.

The catalyst employed in the preferred method may be a modification of the same base catalyst. The base catalyst is prepared as a precipitated iron oxide which analysis indicates to be FezOa with only traces of other metals. The catalyst is formed in a compression pelleting machine into cylindrical pellets about one-eighth of an inch in diameter and about one-eighth of an inch in height. Into each catalyst bed comprising a volume of 56.5 cubic feet, about 7,500 pounds of catalyst are charged. The reactor is part of a system such as disclosed in the drawing.

The catalyst is then dried, for example by passing the gas over the catalyst at a temperature of about 250 to 300 F. for about 3 hours. The drying and the subsequent reactions are most conveniently carried out by introducing the gas separately into the bottom of the reactor and removing the reaction or inert gases from the top of the reactor. Hydrogen is a very convenient drying gas because it does not result in the formation of any impurities; however, an inert gas may be used but it must be flushed from the system after the catalyst is dried. At this stage the catalyst in the various beds is in the form of an oxide and may be so used if desired. However, when completely or partially reduced catalysts are to be prepared, heated hydrogen is then flowed over the catalyst at one atmosphere pressure and a space velocity of about 1150. When the catalyst beds have been heated to a temperature of about 510 F., reduction of the catalyst begins to occur. The passage of heated hydrogen in contact with the catalyst is continued until the desired degree of reduction has been attained, the catalyst beds reaching a temperature in the neighborhood of about 650 F. early in the reduction period. The degree of reduction may readily be determined by determining the amount of water which has been formed in the reduction procedure. At times it may be desirable to introduce the hydrogen separately to the various beds or to reverse the direction of flow in order that the rst beds contacted with the hydrogen may not be overheated before the last beds are at the desired temperature condition.

'Ihe procedures just described are followed not only when preparing a catalyst initially but also when readying a catalyst for use after it has been regenerated.

The reactor is placed on stream by introducing hydrogen and bringing the pressure up to about pounds per square inch. Each of the catalyst beds is brought up to the temperature required for the initiation of the reaction, the specific temperatures being in the range of 425 to 450 F. At this time 600 cubic feet per minute of recycled gas are introduced into the reactor at a tempera-ture of about 450 F. This synthesis gas is prepared by recycling 550 cubic feet per minute of recycle gas and adding 50 cubic feet per minute of synthesis gas containing hydrogen and carbon monoxide in a mol ratio of about 25:1. The synthesis gas comprises 3.3 per cent carbon monoxide, 89.9 per cent hydrogen, and the remainder diluents including those hydrocarbons which are being recycled and which are not removed in the final separation step, as will be described below. At the same time, 52 cubic feet per minute of synthesis gas having a hydrogen to carbon monoxide ratio of about 2.5 l, which is the ratio at which the hydrogen and carbon monoxide are being consumed in catalyst beds, are introduced to the second catalyst bed. Synthesis gas is also introduced at rates increasing from 54 to 62 cubic feet per minute to each of the subsequent beds. Initially it is not necessary to remove a large amount of the gases in the side stream, but as the rate of feed introduction is increased the amount oi heat which must be removed is gradually increased under full operating conditions. At this time approximately 30 per cent of the gases passing through the reactor are passed through the rst separator, cooled, 0.30 pound per minute of liquid products including aqueous phase and hydrocarbon materials is removed from the rst separator', and a similar amount of liquids containing hydrocarbons of somewhat heavier molecular weights and higher boiling points i-s removed from each of the subsequent separators. When the rate of feed introduction has been increased to 500 cubic feet per minute, the gases passing through the rst catalyst bed are of the order of 6000 cubic feet per minute and the gases and products from the various stages are increased in like proportions. In the subsequent beds because only a portion of the normally liquid products and the oxygenated products is removed between each bed, the space velocity is increased until in the last catalyst bed the space velocity is of the order of 7,400. The time required to reach full operating conditions depends upon the specic catalyst used and on the composition of the feed and the amount of recycle. At the end of the lining-out period the fresh feeds are being introduced at the reaction initiation temperature into each of the catalyst beds, and the temperature gradient of about 150 F. is being maintained in each of the beds. The inlet temperatures for the various beds are increased slightly as the run progresses in order to counteract the decrease in carbon monoxide conversion caused by the reduction in catalyst activity. The run is continued as long as the conditions of operation described previously are maintained. The most striking indication of unsatisfactory operation is a drop in the mol ratio of hydrogen to carbon monoxide in the reactor feed to the last catalyst bed or even to a bed previous to the last catalyst bed to below 15: 1 caused by a reduction -in catalyst'. activity,... When vthe inlettemperatu-res; have been increased to the rnaximtu-rj.L preferredprv ating temperature. and the hydrogen to, v carbon monoxideratio inthe reactive feed-to thelastbed remains below :1, it isneoessary torcloseldown they unit andreactivatethe catalyst2 The catalyst in; the reactorsgwhich areqto-be` reactivated is their regeneratedl in o, the.. following. manner. The reactor isziiushed with an*y inert gas and, then a smeltstream;` of'air4 (about 65 cubic feet per minute) and a stream-ornitrogen (abouty 180,011,101@ feet; per tenute) are.int.reducedi.4 'the products or regenerationmay bea-recycled to the ca talystbeds at a rate of about; 1599 to, 1756A bio feetrper minute. The catalystpeaktemf perature is about 45.0? F. under these eerlfltensthen gradually.mereeeedf'teielee-ut eet per( minute andv the. nitrogen feed reduced to zero. Therpeak temlerature ofthe catalyst isere-dually increased. tol abmit()a El. where it is maintained throughout most vofv the regeneration period,.- which usually occupies a total-timeI ot about tihcurs. Theregenerated catalyst after successive ori-stream periods is in substantially the same condition as. the.v freshl catalyst introduced into thereaotor.

The cycleoi' operations in thel presentprooefss comprisestheperiods described; a periodici-,drying;` and reducingg the catalyst if a completely; or` partially. reducedcatalyst is used; a lining-out period; a reaction period; anda regeneration period. rI'he lining-out period andthe reaction period, during `both. of which hydrocarbons are produced are. together referred to as. the onstream period.Y

When operating in accordance withv theA invention, conditionsthat should bezobserved car@` fully arethe ratioof hydrogen to carbonmonoxide and the. conversionv of carbon monoxide.

The ratioroi hydrogen to carbonVnfionoxideisin-l dicative ofthe activity of the catalyst andcar.-

bonmonoxide conversion and is of course depen.

dent upon the compositionY of the gases fed, to thevarious catalyst beds. Accordingly, the=con trol` of the process can be effected .by keeping the amount of hydrogen added between beds constant and varying conditionsl iny accordance with the change inthe mol ratio of` hydrogen to carbon monoxide in the. reactor. feed. For example, aspointed out above, if therhydrogen to carbon monoxide ratio in the reactive .feed to the last catalystbed fallsbelow 15:1, the ratio may be increased by increasing` theratio oiA hy,- drogen to carbon monoxide in the initial feed to the reactor,V The ratio may also beincreased` by increasing the initial temperature. neach of the catalyst beds. However, if the increase in the hydrogen to carbon monoxidel ratio of the entering gases or theA increase in temperature is not elective to raise4 thel hydrogen to carbon monoxide ratioin the gases fed to thevv last catalyst bedto above 15:1 either theamount of hydrogen added between beds may be irlcreased or if the carbon monoxide conversion` is below 95 .perfcent,v thenthe onrstreaini periodfor the reactor should beA discontinued 4and the catalyst regenerated vor replaced.VV

It will be understood that the conditions;dis;vv closed may be varied withinl the scope; *off the; invention.v WhileY itis generally Ypreferredto carry out the process ata pressure of about150. pounds per square inch, other superatmospherioy pressures may be used, such as pressureswithin therangeof about -,to165Qv-poundsfper squareV inch. Because pressure does, not appear.. to.; have;

pleyedfend eteneeenemieel throughput etlewerv space velocities. Y

We have--stated-thet the. initial. reactor. feed. should be heated prior to beingcontactedgwith the catalyst at least to the reaction initiation tempera-ture,l whiclrvariee depending upon the specific Catalyst employed and. the activity ofthe. Catalyst...`

We haveY also Y statedthat aside stream: is removed from the main stream after ythe reactive Vo aseshave passedlthrough the rstcataf lystbed The sidestreamis cooled, liquid procluctsl are removed, a make-up gas comprising-r carbonA monoxide is-I added, the side stream isv again mixed with the., mainstream and theV reactive mixture is introduced to the second cata-V lystv bed. A temperaturev responsive means is placed near the bottom of the second.-bed and this controls the amount of cooling of the side stream removed from the rst'bed. In like man-` ner a side streaml is removed from the main stream from eachvcatalyst` bed and cooledas, determined bythe temperature'of thesucceeding bed.

monoxide.` We have` also stated that the process can be carried outA so as to compensate for a decrease `in activityoi the cat alystbyh increasingy the temperature during an4 ori-stream period.I While hydrocarbonscan be produced underl other. temperature conditions, in general we. prefer to maintain this reactor feed or inlet temperature when usingy a partially orA completely reduced iron catalyst Withinthe range o1" about 4:30 t0, about 475. thel lower temperatures being; em-

ployedwhen the catalyst is relatively fresh, either a.: new catalyst or regenerated catalyst, and the temperature beingr graduallyl increasedtowards thelater part of arun,` When us1ng; aniron oxide catalyst we have round. that ordinarily reaction is not initiated unlessthe reactor feed is heated atleastto about i909 F.,and better about 500 F. ,Duringya` run this .temperature is preferably increasedbut the-maximum should notordinarily exceed about 530"v F. v Y

Fromthe foregoingydescription it willbe seen thatby practicing the present process hydrogen andscarbon monoxidefcan be eiiiciently converted into desiredhyorocarbons andy oxygenated'` cornpounds in a serieslorv catalyst beds while assuring Suestentiel Catalyst. lire.tnrous h erect-ive.l ceri.- trol or' the ,heat created in the exothermic reactions taking place. As previously stated, thereon,-v trel ofthe temperature. of agli/er1 Catalyst bed is accomplished. by. Veryins.;theamount. or the reaction Dr0$1uf2ts;leevir1a thefpreeedirlg bed rer-v mOi/ed` in .e side; streamen@ subjected te; cooling.

Orthedesree ef.- eeelins-Ofthei side. strea ora both, It e willbe.,r understood that .when r reference g isrnade; in .the clairnsl to controlling; the amount;

of. fheatremeved. from. a side. stream, variation A,in the quantity ofgasesrernove-d in such-,side; 'S ,t1eam, the degreeof/coolingvof the sderstream, .012 both, is intended. Ink each casethe, total quantityoi heat requiredA to `be removedwill be, affectedl by.

theftemperatllreand `quantity of; make-up. gas@ 'the mane-up gases. added tol the., side stream: may alsol ccmprisehydrogen and carbon added between beds. However, since any variation in the heat content of the make-up gas will aiiect the temperature of the following bed, the temperature of the reaction mixture contacting that bed will be quickly adjusted to the desired reaction initiation temperature by operation of the control procedure described.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A process comprising passing into contact with a series of beds of synthesis catalyst maintained at hydrocarbon synthesis temperatures and superatmospheric pressures a reactive mixture comprising hydrogen, carbon monoxide, and recycled gases, removing the partially reacted gases from each of said catalyst beds, withdrawing a side stream of partially reacted gases from between catalyst beds while passing the main stream of partially reacted gases towards the succeeding catalyst bed, cooling said side stream, introducing make-up gas comprising carbon monoxide into said side stream, mixing the resulting cooled side stream with the main stream of partially reacted gases, passing the partially reacted mixture at a hydrocarbon synthesis initiation temperature into contact with the succeeding bed of catalyst, varying the amount of heat removed from said side stream in accordance with variations in temperature of said succeeding catalyst bed, discharging the reacted gases from the last catalyst bed, cooling said reacted gases to condense liquid products formed in the reaction, separating from resulting cooled reaction products the condensed liquid products, and recycling a portion of the remainder of the reaction products into contact with said series of catalyst beds in combination with fresh feed to form said reactive gas mixture.

2. The process of claim 1 in which the make-up gas comprises carbon monoxide and hydrogen.

3. A process comprising passing into contact with a series of beds of iron synthesis catalyst maintained at hydrocarbon synthesis temperaturcs and superatmospheric pressures a reactive gas mixture comprising hydrogen, carbon monoxide, and recycled gases, removing the partially reacted gases from each of said catalyst beds, withdrawing a side stream of partially reacted gases from between catalyst beds While passing the main streamV of partially reacted gases towards the succeeding catalyst bed, cooling said side stream to condense liquid products in said side stream, separating said liquid products from the remainder or said side stream, introducing into said remainder of said side stream make-up gas comprising carbon monoxide, mixing said cooled remainder of said side stream with said main stream, passing the resulting mixture at a hydrocarbon synthesis initiation temperature into contact with the succeeding catalyst bed, varying the amount of heat removed from said remainder of said side stream in accordance with variations in temperature of the succeeding catalyst bed, discharging the reacted gases from the last catalyst bed, cooling said reacted gases-to condense liquid products formed in the reaction, separating from resulting cooled reaction products from the last catalyst bed said condensed liquid products, andrrecycling a portion of the remainder of the reaction products into con- 12 tact with said series of catalyst beds in combination with fresh feed.

4. The process of claim 3 in which the makeup gas comprises carbon monoxide and hydrogen. 5. A process comprising passing into contact with a series of beds of iron synthesis catalyst maintained initially at a temperature of from 430 to 525 F. and at superatmospheric pressures a reactive gas mixture comprising hydrogen, carbon monoxide, Vand recycled gases under conditions adapted to produce a temperature gradient within each of said catalyst beds of from 125 to 165 F. and a maximum bed temperature of from 610 to 630 F., removing the partially reacted gases from each of said catalyst beds, removing a side stream of partially reacted gases from between catalyst beds at said maximum temperature of from 610 to 630 F. while passing the main stream of partially reacted gasesl at a temperature of 610 to 630 F. towards the succeeding catalyst bed, cooling said side stream to a temperature of about F. to condense liquid products in saidside stream, separating said liquid products from the remainder of said side stream, introducing into said remainder of said side stream a make-up gas comprising carbon monoxide at a temperature of about 100 F., mixing said cooled remainder of said side stream with said main stream, passing the resulting mixture at a hydrocarbon synthesis initiation temperature into contact with the succeeding catalyst bed, varying the amount of heat removed from said side stream in accordance with variations in the temperature of said succeeding catalyst bed, discharging the reacted gases from the last catalyst bed, separating from resulting reaction products from the last catalyst bed the bulk of the C4 and heavier hydrocarbons and oxygenated compounds not previously removed in said side streams, and recycling a portion of the remainder of the reaction products into contact-with said series of catalyst beds in combination with fresh feed.

6. The process of claim 5 in which the makeup gas comprises carbon monoxide and hydrogen.

'7. A process comprising passing into contact with a series of beds of iron synthesis catalyst maintained at hydrocarbon synthesis temperatures and superatmospheric pressures a reactive gas mixture comprising hydrogen, carbon monoxide, and recycled gases, removing the partially reacted gases from each of said catalyst beds, removing a side stream of partially reacted gases comprising from 15 to 35 per cent of the total partially reacted gases from between catalyst beds while passing the main stream comprising the remainder of the partially reacted gases towards the succeeding catalyst bed, cooling said side stream to condense liquid products in the side stream, separating said liquid products from the remainder of said side stream, introducing a make-up gas comprising carbon monoxide into contact with said remainder of said side stream, mixing said cooled remainder of said side stream with said main stream to obtain a mixture at a hydrocarbon synthesis initiation temperature, introducing said resulting reaction mixture into the succeeding catalyst bed, varying the amount of heat removed from said remainder of said side stream in accordance with variations in the temperature of said succeeding catalyst bed, dis. charging the reacted gases from the last catalyst bed, separating from resulting reaction products from the last catalyst bed the bulk of the C4 and heavier hydrocarbons and oxygenated compounds formed in the reaction and not removed in said side streams, and recycling a portion of the remainder of the reaction products into contact with said series of catalyst beds in combination with fresh feed.

8. The process of claim 7 in which the makeup gas comprises carbon monoxide and hydrogen.

9. The process of claim 7 in which the makeup gas comprises hydrogen and carbon monoxide, said mixture comprising hydrogen and carbon monoxide in the ratio at which said gases are consumed in each catalyst bed.

WILLIAM A. HORNE. VINCENT L. CRAWFORD.

14 REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,149,515 Fischer Mar. 17, 1939 2,243,869 Keith, Jr. et a1 June 3, 1941 2,256,622 Murphree et a1. Sept. 23, 1941 2,276,274 Keith, Jr Mar. 17, 1942 2,301,687 Dorschner Nov. 10, 1942 2,318,626 Pier et a1. May 11, 1943 2,411,255 Sensel Nov. 26, 1946 2,433,255 Atwell Dec. 23, 1.947 2,503,356 Sensel Apr. 11. 1950 

1. A PROCESS COMPRISING PASSING INTO CONTACT WITH A SERIES OF BEDS OF SYNTHESIS OF CATALYST MAINTAINED AT HYDROCARBON SYNTHESIS TEMPERATURES AND SUPERATMOSPHERIC PRESSURES A REACTIVE MIXTURE COMPRISING HYDROGEN, CARBON MONOXIDE, AND RECYCLED GASES, REMOVING THE PARTIALLY REACTED GASES FROM EACH OF SAID CATALYST BEDS, WITHDRAWING A SIDE STREAM OF PARTIALLY REACTED GASES FROM BETWEEN CATALYST BEDS WHILE PASSING THE MAIN STREAM OF PARTIALLY REACTED GASES TOWARDS THE SUCCEEDING CATALYST BED, COOLING SAID SIDE STREAM, INTRODUCING MAKE-UP GAS COMPRISING CARBON MONOXIDE INTO SAID SIDE STREAM, MIXING THE RESULTING COOLED SIDE STREAM WITH THE MAIN STREAM OF PARTIALLY REACTED GASES, PASSING THE PARTIALLY REACTED MIXTURE AT A HYDROCARBON SYNTHESIS INITIATION TEMPERATURE INTO CONTACT WITH THE SUCCEEDING BED OF CATALYST, VARYING THE AMOUNT OF HEAT REMOVED FROM SAID SIDE STREAM IN ACCORDANCE WITH VARIATIONS IN TEMPERATURE OF SAID SUCCEEDING CATALYST BED, DISCHARGING THE REACTED GASES FROM THE LAST CATALYST BED, COOLING SAID REACTED GASES TO CONDENSE LIQUID PRODUCTS, FORMED IN THE REACTION, SEPARATING FROM RESULTING COOLED REACTION PRODUCTS THE CONDENSED LIQUID PRODUCTS, AND RECYCLING A PORTION OF THE REMAINDER OF THE REACTION PRODUCTS INTO CONTACT WITH SAID SERIES OF CATALYST BEDS IN COMBINATION WITH FRESH FEED TO FORM SAID REACTIVE GAS MIXTURE. 